Huge study shows how a major religion spread around the world, and some things never change

If you’re out to start a religion, it might be more important to aim high rather than wide and sign up the big names first.

That’s the take-home message from a study on the history of Christianity, which found its reach across the globe had less to do with the hoi polloi spreading the word, and far more to do with powerful leaders exercising control over small groups – not entirely unlike the way today’s visionaries set out to target influencers.

An interdisciplinary team of researchers from around the globe have weighed in on a discussion over whether Christianity grew as a result of top-to-bottom or bottom-to-top cultural forces.

The question concerns more than just the emergence of a single religion.

Vanderbilit University biologist Nicole Creanza wasn’t involved in the research, but summed up the study’s findings in an accompanying Nature commentary.

“If we know enough about a population, can we predict how quickly it will adopt a certain idea?” says Creanza.

It turns out we might not need to know very much at all.

A study led by Joseph Watts from the Max Planck Institute for the Science of Human History analysed several centuries of well detailed historical records from a database of Austronesian cultures.

These communities consist of diverse pockets of a distantly related people descended from a Taiwanese population, spreading as far west as Madagascar and as far east as Rapa Nui.

Between the 16th and 19th centuries, Christianity was adopted as a central faith by these disparate cultures under the influence of travelling European missionaries, with most converting within a narrow window of just three decades.

The diversity of Austronesian cultures and the fact their conversions were recent and well documented provide for a perfect opportunity to test several hypotheses on the spread of a significant belief system.

From small beginnings as an offshoot sect of Judaism more than 2,000 years ago, Christianity has come to be the world’s most popular religion with more than 2 billion adherents.

Exactly what fuels its growth has been the subject of a great deal of debate. Is it the enforcement of political systems, or grass roots activism? Does social inequality have much to do with it? Does population size matter?

The researchers used a variety of statistical measures to compare the rate at which Christianity’s adoption with various sociocultural characteristics.

Surprisingly, social inequality had little to do with conversion, in spite of the religion’s origins among social underdogs.

Christianity seemed to spread fastest under the influence of strong leaders holding sway over small clusters of loyal subjects.

“We note that the two cultures that took the longest to convert in this study – Ifuagao and Iban – lacked any form of political organisation,” the researchers wrote in their report.

The research paints a picture of missionaries learning to win favour with key figures in close-knit communities, providing them with material goods and trade opportunities.

Of course, this was also a solid survival strategy as much as a missionary goal – it pays to have powerful friends if you’re new in town.

But those robust political structures helped carry Christianity further and faster than missionary boats.

Smaller groups of people were also more likely to notice changes in their neighbours’ behaviours, a feature described as frequency-dependent cultural transmission.

The study is far from the final word on how major cultural systems like religions compete and convert one community over another. But it does help provide evidence describing the important factors at work.

The question of whether or not inequality matters, or whether it’s more chicken or more egg, has also attracted a great deal of attention over the years.

A recent study by anthropologists and health scientists from the University of Bristol in the UK and the University of Tennessee in the US has challenged earlier conclusions that those in poverty tend to turn more to religion.